In an existing refrigeration system, heat exchange tubes of an evaporator and a condenser are generally hollow round tubes or flat tubes. A fluid in a single state flows through the same heat exchange tube, and although multiple heat exchange tubes can form and include multiple channels and thereby form different flow paths, there is an equivalent parallel-connection relationship among the multiple flow path channels, and the states of fluids entering the channels are substantially the same. Merely serving as the same flow path.